There are a number of ground anchors available on the market with different configurations and applications. Some ground anchors are designed to assist with moving a stranded vehicle, most commonly in off-road use, when a vehicle becomes immobilised, and no natural anchor point is available.
One type of vehicle recovery ground anchor that is commonly used is a pole and rope system. In this system, an end of the pole is inserted into the ground, in front of the stranded vehicle. The first end of a rope is then attached to the exposed end of the first pole, and the second end of the rope is attached to the top of a second pole that is inserted into the ground. With the rope attached, the second pole is inserted into the ground, in a line parallel to the first pole. The rope and pole attachment is then repeated with a second rope and third pole, and the third pole is attached to a winch on the vehicle via another rope. By using a number of poles, this system acts to distribute the load between the poles, and provide additional support. However, this system has a number of disadvantages. For example, the anchor only provides a limited amount of support before the poles are pulled from the ground by the load incurred once the vehicle is winched forward. This is due to the angle of force applied to the anchor and the shallow placement of the poles, into the ground. As may be appreciated from the above, this rope and pole arrangement can be complicated to set up, as the right angles for the poles and rope need to be found before sufficient support can be found. The arrangement also requires the user to carry three poles, rope and a means for inserting the poles into the ground, such as a sledge hammer. Therefore, this anchor system can be bulky and heavy to transport.
Other common types of vehicle recovery ground anchors available use a triangular plate that furrows into the ground. Examples of this system include; The Pull-Pal® Ground Winch as described in U.S. Pat. No. 5,850,715, the SARCATM Portable Rescue Tree™, and the Straight Forward™ ground anchor. These systems all use a triangular plate with at least one attachment arm and a line. When in use, a pulling force is applied to the line via a winch on the vehicle, which then pulls onto the arm and plate, causing the anchor to furrow into the ground. One disadvantage of these systems is that they are bulky and heavy owing to the high degree of strength required from the assembly when a load is applied. In addition, these systems may only be used in specific terrains. If the ground is too hard, the tip of the plate has to be manually inserted into the ground, before the anchor can be used. If the ground is too soft, such as in sand, the anchor is pulled through the ground, rather than fixing in position to act as an anchor point. Additionally, all of the above systems have a limited range of depth that the anchor can penetrate the ground, therefore resulting in these anchors gripping the softest top soil.
Other systems that are also available on the market, which penetrate at a deeper level, involve a shaft and auger combination, with a line attached to the shaft. One problem with these anchors is that the line is prone to twisting around the shaft, when the shaft is twisted into the ground. To address this problem, some alternative configurations have been developed.
U.S. Pat. No. 6,824,331 (US'331) describes a configuration with a hollow shaft, where the line runs through the shaft aperture and attaches. to the auger. A problem with this configuration is that when the anchor is in use, the force is applied to the anchor above the ground; this reduces the amount of force that can be applied to the anchor, before the anchor is pulled up out of the ground.
U.S. Pat. No. 5,927,905 is another shaft, auger and line system. The line is coiled around a portion of the shaft, close to the auger at one end of the shaft-before extending up through the shaft. This system has a similar problem to the anchor described in the US'331 patent, as the line is attached to the ground anchor above the ground. This configuration also increases the chances of the coil becoming stuck and tangled in the shaft or surrounding soil, or the anchor being pulled up out of the ground.
A number of other systems, such as those described in U.S. Pat. No. 5,930,959 (US'959) and U.S. Pat. No. 2,603,319 (US'319) attach the line close to the auger portion without running the line through the shaft. As shown in US'959, the line is attached in the middle of the auger. Although there is a gap in the auger blades, this configuration still has a problem of the line getting caught and even bent or cut by the auger blades, particularly if the anchor needs to be screwed in further and/or when the anchor is removed from the ground.
The anchor-described in US'319 attaches the line to a swivel portion above the auger portion. This system allows the line to swivel around the shaft without getting caught and wrapped around the shaft. However, the line is only attached by threading and tying the line through a hole in the swivel portion. Although this configuration may prevent the line from wrapping around the shaft, there is still a chance that the swivel portion may jam, subsequently causing the line to start wrapping around the shaft. This connection technique suits a permanent installation, or light load application, under heavy load conditions the anchor could fail to hold due to the connection between the line and the swivel portion. As the load is applied the section of line through the hole will tend to kink thus weaken the line (there is no easy way of using a thimble to prevent this). In addition the method of connecting the free end of the line to form the loop needs to be carefully chosen so that it does not reduce the strength of the line significantly. Only wire rope clips are shown or described in US'319, and these are one of the few connection devices that can easily and quickly be used for forming a loop in a line without specialist tools so this makes sense, other methods are available but most of these are permanent. To operate correctly and maintain maximum strength clip manufacturers prescribe the number and spacing of the clips required to form a strong joint. Even properly used (the bolts tightened with a torque wrench) they have an efficiency of around 75%-85% of the original line breaking strain thus any operation close to this could cause the clips to fail. In a vehicle recovery situation it is unlikely that wire clips will be properly applied, given the number, spacing and assembly requirements. If clips are used most manufacturers do not recommend they are reused this increases the cost if the cable is not permanently connected to the cable. This configuration also has a point of weakness where the line is attached to the shaft. Therefore, only a small amount of force can be applied to this anchor, before the anchor is pulled out of the ground.
Additionally, all of the above systems are designed for light work, as the systems incorporate light weight components and a light rope that would be easily pulled up out of the ground, under heavy load.
Therefore, it should be appreciated that it would be an advantage to have a device where the ground anchor can easily insert into the ground, without the cable breaking, being bent or damaged, or twisting around the shaft. It would also be an advantage to have a device that was lightweight, and yet provides the strength and ground holding ability to withstand the forces applied when winching a stranded vehicle. Also, having an anchor that could be used in various types of terrain, such as both hard soil and sand, would be an advantage. It would further be an advantage if the device could be releasably connected to a cable with a loop at one end.
It is an object of the present invention to address one or more of the foregoing problems or at least to provide the public with a useful choice.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
It is acknowledged that the term ‘comprise’ may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term ‘comprise’ shall have an inclusive meaning—i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other non-specified components or elements. This rationale will also be used when the term ‘comprised’ or ‘comprising’ is used in relation to one or more steps in a method or process.
Further aspects and advantages of the present invention will become apparent from the ensuing description which is given by way of example only.